Sunday, February 27, 2011

New published article (Part 1): herpetocetine jaws, and an example of finding a "simple" research project

The new issue of PaleoBios, the paleontology journal published by UCMP at UC Berkeley, includes my new article on herpetocetine jaws from the Santa Margarita Sandstone in central California. During the fall of 2008, I was in my first semester of graduate school, and was taking a difficult, time-intensive course on advanced stratigraphy. At the time, I already had two articles I had been working on: one on my undergraduate research concerning a new fossil vertebrate assemblage from the Purisima Formation, and another on Plio-Pleistocene fur seals from the Wildcat Group in northern California (both are currently in press). However, neither was in any shape to be published anytime soon - one was only half written, and the one that was nearly finished needed a lot of work (i.e. quality control). I needed a new manuscript to work on, to give me something to do that semester aside from stratigraphy, which had started to eat away at my brain. In other words, I needed to start something fresh from scratch, with a clear beginning, a clear end, and a clear message.

The right dentary of UCMP 85431. Scale bar =10cm. From Boessenecker (2011).

A month earlier, I had given a presentation (coauthored with Jonathan Geisler) on a new skull of Herpetocetus bramblei I had collected from the Purisima Formation in 2007. While ruminating on possible projects, I suddenly remembered a partial lower jaw from the Santa Margarita Sandstone that looks a lot like the lower jaw of Herpetocetus*. The problem is, the Santa Margarita Sandstone is early Late Miocene in age (10-12 Ma), while the oldest known bona fide specimens of Herpetocetus are latest Miocene to earliest Pliocene in age (~5 Ma). In fact, the oldest known described specimen is the fragmentary type specimen of H. bramblei, which is right about 5.33 Ma. So, this specimen (UCMP 85429) is MUCH older than any known specimen of a "true" Herpetocetus.

*All species of Herpetocetus have relatively similar lower jaws, and currently the lower jaw has only been described for the type species, Herpetocetus scaldiensis (the type specimen of which is a lower jaw - more on this later).

The left dentary of UCMP 85429; scale bar = 10cm. From Boessenecker (2011).

The lower jaw of baleen whales has long been assumed to be a fairly diagnostic element, at least in certain groups. Herpetocetus scaldiensis certainly has a very distinctive mandible. Other fossil mysticetes certainly have distinctive mandibles as well. Many fossil mysticetes (H. scaldiensis, Balaenoptera davidsonii, Archaeschrictius ruggieroi, etc.) have been described just off of their lower jaws. Are dentaries really that diagnostic? Perhaps. Demere (1986) used mandibular features to reevaluate "Eschrichtius davidsonii" from the San Diego Formation, which was a chunk of a 30% complete mandible, missing the anterior and posterior ends. Being able to refer a new dentary to this taxon, he demonstrated that the "davidsonii" morphotype was actually a rorqual, and assignable to the genus Balaenoptera, which led to its recombination as Balaenoptera davidsonii. Clearly, mandibular morphology is important, and can be used to assess the taxonomy of certain groups, and 'fix' the taxonomy of certain problem taxa. Are these specimens the oldest known records of Herpetocetus?

Reconstructed lower jaw of Herpetocetinae genus and species indet., based on UCMP 85429 and 85431. From Boessenecker (2011).

Reflecting upon the known fossil record of "true cetotheres" - relatives of Cetotherium and Herpetocetus (an entire other topic worthy of its own post) - I was able to formulate some interesting questions I could ask (and attempt to answer), which would make a nice core of an article. With these objectives in mind, I started taking copious notes on the anatomy of the fossil specimens, and eventually typed these notes up into an anatomical description for the article. By the end of the semester, I had a manuscript that was about three-quarters finished. During spring 2009, I wrapped up the discussion, and constructed some figures. I had a few people look at it and make some comments. Morgan Churchill looked at it late in spring, and had some of the most constructive and useful edits. That summer, I TA'd the Geology Field Course for MSU, and during some of the weeks, I took my manuscript out into the field with me, along with a red pen. In between helping students, I sat out in the hot sun, and critically examined every sentence in the manuscript. I even drafted one of the figures (on vellum, with nice pens) around the campfire one night after a few beers. By the end of the second to last project at field camp, I had all my edits finished, and I sent it off to PaleoBios for review.

To be continued...

Boessenecker, R.W. 2011. Herpetocetine (Cetacea:Mysticeti) dentaries from the Upper Miocene Santa Margarita Sandstone of Central California. PaleoBios 30:1:1-12.

Deméré, T.A. 1986. The fossil whale, Balaenoptera davidsonii (Cope 1872), with a review of other Neogene species of Balaenoptera (Cetacea: Mysticeti). Marine Mammal Science 2:277–298.

Saturday, February 26, 2011

New artwork II: 'rediscovered' specimen drawing

About two months ago, I was cleaning off my desk and found a sheet of vellum paper with an old specimen drawing I had done. This drawing was is of a pair of associated dentaries of the Pliocene fur seal Callorhinus gilmorei. I first presented on this fantastic specimen on my 2007 SVP poster at the Austin, TX meeting.

Unfortunately, I discovered this about three months after my manuscript describing this fossil was accepted in JVP, and there was no way to include it in the published article. To be honest, I could probably do better now, but I think it turned out reasonably well for a journal article figure. In the future I'm going to do a lot more technical illustrations of individual specimens, partly as practice, but also to showcase myself.

Stay tuned! The article will be published in the March 2011 issue of JVP: that's sometime in the next couple of weeks. (Holy god, it's March in only 48 hours!). More artwork is on its way.

Boessenecker, R.W. In Press. New records of the fur seal Callorhinus (Carnivora: Otariidae) from the Plio-Pleistocene Rio Dell Formation of Northern California and comments on otariid dental evolution. Journal of Vertebrate Paleontology 31:2. 14pp.

Thursday, February 24, 2011

New artwork I: Cynthiacetus reconstruction

Hey folks,

Some of you cetophiles may have already seen photos of this specimen floating around on the internet. I thought the mount was pretty dynamic, and would work well as a skeletal reconstruction - so I did it. A photo of this specimen which has thus far only been identified as cf. Cynthiacetus is featured in a recent paper by Christian de Muizon.

Cynthiacetus is a dorudontine archaeocete that was originally described from the Eocene of Mississippi by Mark Uhen. He also referred a few vertebrae and a partial skeleton to this taxon from the Eocene of Egypt. This new skeleton (and I am not sure how complete it is) is from the Eocene of Peru, and is part of a large new collection of Peruvian archaeocete cetaceans we will be hearing about over the next few years.

Return to the thanksgiving odontocete locality

Over winter break Chris Pirrone and I returned to the locality where, a month prior, we had excavated a complete odontocete skull. If you recall, when we collected the specimen we had to excavate and pedestal the skull sideways, rather than the normal way (downwards) that most paleontologists are used to. When I had seen the skull at the end of the summer, it was only a few feet above the sand. I knew that over thanksgiving, there would be a very good chance that the sand would all be gone due to the rough weather which tends to erode away the beaches.

Luckily, at thanksgiving there was a three foot-wide 'rim' of the summer beach left, and closer to the ocean, the beach sand was about 8 feet lower. Fortunately, we had just enough time to collect the fossil. When we returned in January, this sliver had been completely eroded away, leaving the excavation pit about 9 feet above the beach and well out of reach. In the above photo, you can see it about left center.

And here I am pointing to it. It would still have been accessible by ladder, but that would have been a real pain, and I'm pretty sure after standing on a ladder for five hours, it's almost a guarantee that you'd fall off.

Comparison between Thanksgiving 2010 and January 2011. The two photos are taken from nearly the same position (note the rock in the foreground) but the more recent photo is taken from further away from the cliff.

Otherwise, after initial preparation, the fossil appears to be a juvenile Parapontoporia, with a partial dentary, and both tympanoperiotics. The tympanoperiotics are now fully prepared, and were articulated, and sitting above the bony nares and the vertex of the skull (i.e. in contact with the dorsal surface). As the skull was upside down, the earbones must have fallen out, and then the skull rolled over on top of them. I'll have pictures soon.

Saturday, February 19, 2011

Trip to New York

New York City and Central Park from the 4th Floor of the
American Museum of Natural History.

A few weeks ago I took a trip to New York in order to be officially hired as a writer for a website on whale evolution that Jonathan Geisler (New York College of Osteopathic Medicine) is collaborating on with John Gatesy (UC Riverside) for an NSF grant. This trip was convenient because Jonathan and I are collaborating on a couple of research projects together, including the description of a fragmentary pilot-whale like skull from the Purisima Formation, as well as working on a large body of Herpetocetus material from Northern California. Once the website is up, I'll go into quite a bit more detail about it.

In 2008 I presented a talk (my first oral presentation) at SVP on a new skull of Herpetocetus bramblei I had found the previous year. The skull is pretty nice, and has about half the rostrum and a complete braincase, with earbones (tympanic, petrosal, stapes, incus, malleus). Because of its completeness and preservation, it will be a daunting task just to describe it. Fortunately (or unfortunately, depending upon how you look at it!) I have since collected another skull with a complete rostrum, and another (slightly less complete) skull from higher up in the Purisima Formation which may represent a younger species. So, including a fragmentary braincase at UCMP, there are four Herpetocetus crania, about a dozen petrosals, several tympanics, a half dozen dentaries, and some postcrania that we need to describe. Anyway, we didn't really work on this project at all.

One day during the trip we went in to the AMNH to look at some modern odontocete crania for comparison with the fossil pilot whale. A year and a half before, when I presented my poster on it at SVP (the 2009 Bristol meeting), I had identified it as Globicephala sp. at the time; fossil delphinid expert Giovanni Bianucci mentioned to me that he was not quite convinced that it belonged in that taxon. At the time I just identified it as best I could, without really having access to crania of other globicephalines like Pseudorca, Peponocephala, and Feresa. During our AMNH trip, we came to a similar conclusion as Giovanni - it's got too many differences to be in Globicephala, as it shares some other similarities with Pseudorca and Feresa.

Jonathan Geisler puzzles over fossil and modern globicephaline skulls.

However, it still definitely falls within the clade Globicephalinae, and that's what's important any way. I'll go into more detail about the ramifications of this fossil later on once we've at least submitted our paper - hopefully sometime early summer I'll have this one (manuscript #6) off.

Here I am (with appropriate shirt for the visit) with a beluga (Delphinapterus) skull.

Perhaps in a later post I'll post some of the pictures I took on a 15 minute dash through the fourth floor exhibits (which was all the time I had before we wanted to leave).

Monday, February 14, 2011

Nobody likes Aetiocetus =(

I randomly came across this while trying to look up information for a summary about Aetiocetus weltoni I'm writing for a webpage (more info on the new webpage soon!).

Anyway, I became the first person to officially 'like' Aetiocetus. Please think of the toothed mysticetes; the Aetiocetus weltoni holotype specimen is alone this Valentine's Day. Please show Aetiocetus some love.

Broken tailbone

I failed to mention this a year ago when it happened, but during spring break last march (2010) I broke my tailbone way up in a quarry in the Santa Cruz mountains. I was sliding down a steep gulley carved in the Santa Margarita Sandstone, attempting to access a bonebed. I can't even remember if I got anything or not, but at one point, I realized I could not go back up as I had done before.

The dreaded gulley I dropped out of, right onto my #@!.

I looked below me - I had another ten feet of gulley or so before it dropped off. It looked like a large talus cone of sand about fifteen feet below me, which is also exactly what you'd expect, you know, at the bottom of a gulley like that. It looked like a six foot drop or so, nothing bad - I've jumped off cliffs down to the beach from a little bit higher with no consequence, so I thought I might as well. So I slid down to the end, and dropped down, with both toes pointed downhill. Only, the drop ended up feeling a little longer than 6 feet. When I landed, my feet bounced off the "talus cone", which was in fact a thin (1 inch?) veneer of sand over a smooth sandstone surface, my legs flew up in the air, and I fell back onto my tailbone. Now, this wasn't like my feet slowed me at all - all this took place within a second, and I effectively fell the entire distance with my tailbone intercepting 90% of the impact.

The red line shows the distance I fell onto my tailbone.

Naturally, I sat there writhing in pain for a good fifteen minutes, after I crawled out of the hot sun. Luckily no one was in the vicinity (it was pretty embarrassing), or perhaps if they were, they were driven away by a ten minute string of expletives. I've never broken a bone before (except a possibly less serious tailbone break during a snowmobile mishap in 2006), and I gotta admit, the pain was pretty intense. It's strange, it was really dull, but so intense it made me nautious for the better part of two hours. It took a while before I felt like I wouldn't puke from it. And damnit, I had just eaten a nice homemade lunch - I didn't want it to go to waste! Fortunately, after a while I kept on prospecting, and found a beautiful partial Imagotaria downsi (early walrus) dentary.

Chris Pirrone surveys the dreaded quarry.

In December I returned to the locality with my buddy Chris Pirrone, and we found a LOT of bone. It appeared as though an entire mysticete dentary (the single largest bone to ever evolve) that had formerly been about 5 or 6 feet long had eroded out of the cliff into about thirty pieces and was beyond salvage. However, we did find what appears to be an Imagotaria metapodial, which will be nice when I get it prepared. Anyway, I took these photos of the gulley, and when we returned to the site, it looks like I fell 8-10 feet instead of 6. Fun!

Anyway, the day I broke my tailbone, I continued my day and hit up about four more localities - sure, driving was awkward as hell, but standing didn't hurt one bit. In fact, it seemed to help. I actually ended up finding some great stuff that day. I thought about returning home, but I realized all I'd be doing there would be sitting around, which would hurt more than a day of fieldwork along the pretty coastline. What really sucked was the drive back to Montana - I had to pull over every hour and a half or so to get up and walk around.

The moral of the story is: be careful, and don't get cocky (or, overexcited and lose track of your surroundings). And if you must do what I did, land sideways with one foot downhill, like you're surfing. Never go face down, or facing the cliff (I can imagine a faceplant into the rock wouldn't be too nice). Or tuck and roll.

It's now 11 months later, and my tailbone still hurts if I sit in a bad chair for a couple hours.

Thursday, February 10, 2011

Mammal bite marks on fur seal bones, Part 3

Within 48 hours of my paper being published, I tried seeing if I could find anything if I searched for 'pinniped bite marks' on google. Sure enough, I saw that Dr. Alton 'Butch' Dooley had already covered it (thanks, Butch!), but I saw something else that made me angry and very excited at the same time. This was an article on feeding damage induced by a leopard seal attack on a human.

Pair of tooth punctures from the leopard seal attack.

Yes, the loss of human life is very tragic and all, but this is really exciting! As aggressive as leopard seals are (and as bad a rap as they get in movies like March of the Penguins and Happy Feet), and as scary as some other pinnipeds are, they normally don't attack humans, and if anything are typically wary of humans. This attack involved the 28-year old Kirsty Brown, a scientist in Antarctica, who was snorkeling at the time. The seal attacked her, and dragged her under water for 6 minutes to a depth of 70 meters (!). That's pretty incredible. Observers estimated the seal was 4-4.5 meters long.

What is most interesting about this paper is that the punctures figured above in the article are very similar to those that Frank Perry and I described (Boessenecker and Perry, 2011). The bite mark on the radius is most similar, as the puncture penetrated the cortex, and left a peripheral ring of depressed bone, just like these. It is difficult to say because the article did not go into the details much, but although these punctures are undoubtedly canine punctures, they appear much too close together to be from the same bite. Perhaps these were from the same canine on different bites, or something along those lines.

Unfortunately, this paper was published in 2007, and had I known about it, I would have totally cited it. In fact, this paper makes the pinniped origin of the bite marks seem all that more probable. And, on top of that, it also bolsters the case that these bone modifications have been identified correctly. So, my apologies to Guy Rutty; I didn't mean to not cite you, and I certainly wish I had.

Rutty, G.N. 2007. Pathological findings of a fatal leopard seal attack. Forensic Science, Medicine, and Pathology 3:57-60.

Wednesday, February 2, 2011

Mammal bite marks on fur seal bones, part 2

A few months after I collected the radius, I was invited to go examine Frank Perry's private collection. He's donated the majority of his material to UCMP, LACM, and the Santa Cruz Museum, but there was some remaining material. Several specimens he allowed me to borrow and prepare, including a partial juvenile Parapontoporia cranium, a walrus vertebra, and several fur seal bones. One of these was a very small humerus from a fur seal pup, roughly the same size individual as the radius I mentioned earlier. This specimen also happened to have a circular depression with a ring fracture, although it is much more shallow, and larger. This may be attributable to a larger, blunter tooth. Both of these specimens are probably attributable to the species Thalassoleon macnallyae, although in the article the bones are only identified to the family otariidae.
The right radius of a juvenile fur seal in anterior (left) and lateral (middle) views, and a closeup of the bite mark (right).

So, what caused these? Many, many, many studies have been published on shark tooth inflicted bite marks, which are typically linear gouges. These gouges are sometimes associated with removed 'chunks' of bone, but never have any fractures. These are obviously not linear gouges, and instead appear to be the result of the bone surface being pushed in. Circular holes can be caused by boring clams (pholad clams), but these are eroded, and do not result in fracturing. As it turns out, many similar tooth marks have been reported for conical mammalian teeth, of terrestrial mammalian predators and scavengers. One single similar tooth mark has been reported for a marine mammal: a skull of a juvenile sea lion (Eumetopias) from the Pleistocene of British Columbia (see the paper for more comments on this article). In fact, this is only the second reported occurrence of probable mammalian bite marks on fossil marine mammal bones.

Figure 2 from Boessenecker and Perry (2011) showing the bones and bone modifications.

The next question is, what type of mammal has the dental equipment capable of inflicting this sort of damage? Several pinnipeds, including the bizarre walrus Dusignathus santacruzensis, have teeth small enough to inflict these punctures. Most dolphins have teeth that are too small, and too closely spaced to make these punctures. Larger odontocetes, including the beluga relative Denebola, have larger teeth which are spaced far enough apart to form the punctures. Recently, Jonathan Geisler, Frank Perry, and I presented a poster on a pilot whale-like delphinid, and something the size of this cetacean could easily have produced the bite marks. The possibility remains that a terrestrial carnivore, like a canid, felid, or ursid; modern mammalian carnivores often prey upon or scavenge upon pinnipeds on shorelines. Lastly, the fur seal Thalassoleon has teeth that could produce the punctures. But Thalassoleon is the same species, you say! Well, oddly enough, extant fur seals and sea lions frequently commit infanticide - killing juveniles of their own species, sometimes in order to feed, other times as a part of aberrant sexual behavior where juveniles are mistaken for females.

Table of biogenic bone modifications from Boessenecker and Perry (2011) reported from marine vertebrate bones.

Unfortunately, it isn't possible to narrow the possibilities down any further. I'm getting tired, so stay tuned for part 3.

Mammal bite marks on fur seal bones, part 1

It's approximately four in the AM in beautiful Long Island, New York, and this most recent blog post is brought to you by insomnia! I tend to not fare well in unfamiliar hotel rooms unless I'm relatively exhausted. Even though I'm running on a total of four hours of sleep since the night before I flew out to New York, I fared pretty well today. Tomorrow, I have a visit to the American Museum of Natural History in NYC, and Jonathan Geisler and I will be examining globicephaline dolphin skulls; the Globicephalinae are a clade of delphinids (oceanic dolphins) including pilot whales (Globicephala), Risso's Dolphin (Grampus), and false killer whales (Pseudorca). We're working on a short article together on a very fragmentary large odontocete skull from the Purisima Formation in Santa Cruz that shares some features in common with Globicephala.

But I'll talk more about that project later. More importantly, over this last weekend my first article was published - "Mammalian bite marks on juvenile fur seal bones from the late Neogene Purisima Formation of central California", which I coauthored with my friend and colleague Frank Perry of the Santa Cruz Museum of Natural History. And, oddly enough, right as I am typing this up now, I see that my friend Dr. Alton "Butch" Dooley at the VMNH has already beat me to the punchline (thanks for the free publicity, Butch!), and has discussed my new paper on his blog, and compared it with some similar bite marks on proboscidean and chalicothere postcrania. Seeing as this is my first published article, I'll go a bit more in depth this time and post this in two or three parts.

The story starts on Christmas day, 2008. As I've alluded to before, winter is one of the best times to go out to the coast and do fieldwork. I suffered through some pretty intense, cold, biting weather this winter - I do not advise wearing hiking sandals on the beach and crossing streams in 45 degree weather with 40mph wind. That hurts. Anyway, now I'm rambling. I left our annual (gigantic) family Christmas dinner in Marin County and went to bed early, planning to take advantage of a favorable tide the day after Christmas. While out on the coast, I saw a boulder of a shellbed that is not normally accessible that had fallen on the beach, and a cute little brown object sticking out of it. Enough was exposed to identify it as a radius (forearm bone) of a juvenile fur seal. The specimen is tiny, and is only 69mm in length; this specimen, however, is lacking the proximal and distal ("elbow" and "wrist" ends of the bone, respectively) epiphyses (epiphyses are the ends of long bones which at birth are unfused, and fuse onto the middle 'shaft' of the bone later in life; the joint they fuse at is sometimes called the 'growth plate', and the fusion of epiphyses is what results in the decreased number of bones in adults relative to the higher number of bones in infants).

The fossil fur seal radius, UCMP 219009, in lateral (left), medial (center), and a magnified image of the bite mark (right).

When I prepared the bone from the soft shelly sandstone later that evening, I found a strange hole on the medial (medial means the side fo the radius closer to the body) side of the bone. This hole had a ring fracture around it, and a depressed ring of the bone's surface was adjacent to the hole itself. Pushed down into the hole was a fragment of the bone surface that had formerly occuppied the middle of the hole. Most importantly, when I prepared this fossil, there was sandstone filling in this feature, and because I was very careful and collected the bone in a block of sandstone, I knew that I had not damaged the specimen, and that this feature had not been formed after fossilization (i.e. it could not have been damaged when it was exposed, because the side with the puncture mark was embedded in sediment). Additionally, there were no hard objects such as a pebble or a shell that could have been pushed into the bone surface - sediment becomes compacted after burial, due to the immense pressures induced by trillions upon trillions of tons of rock overhead. Diagenetic compaction could push a pebble or an invertebrate shell into the bone surface and cause a similar puncture mark. Incidentally, bone can as well - a cranium of Herpetocetus bramblei I am working on describing with Jonathan Geisler has a similar puncture to those reported here, but the end of the jugal bone actually was lodged into the hole, probably as a result of diagenetic compaction. That would make a great paper, too, come to think of it...

Needless to say I was pretty confused at first, and I held off on interpreting it immediately, until I had read some more literature in order to come to a more informed decision on what I thought it was. I've written enough for now, so I'll continue this in a following post.

See also: Dr. Alton Dooley's blog post about this and other bite marks at Updates from the Vertebrate Paleontology Lab.

Boessenecker, R.W. and F.A. Perry. 2011. Mammalian bite marks on juvenile fur seal bones from the late Neogene Purisima Formation of Central California. Palaios 26:2:115-120. Abstract. Paper at